Growth Of Rods Research Articles

Formation Mechanism and Properties of Foam-Structured ZnO Films Prepared Using Catalyst-Free Carbothermal Method

Foam-structured ZnO films were formed on c-axis Al2O3 substrates by using a catalyst-free carbothermal method. The morphological properties of the films strongly depended on their substrate position in the reactor, implying that the quantity of Zn vapor transported played a crucial role in determining the film structure. The formation mechanism of the films is proposed to be as follows: with increased transport of Zn vapor, vaporized Zn elements transformed into liquid Zn nanoparticles, and the liquid Zn elements on the rods promoted the new nucleation of ZnO nanorods. The repeated growth of ZnO rods at the nucleation sites led to the foam-like structure. The as-formed foam-structured ZnO films exhibited the wurtzite crystal structure, and the atomic composition ratio of Zn to O was 1 : 0.85. The main photoluminescence emissions were centered at 3.3 and 2.5 eV, and they were attributed to band-to-band and defect-related transitions, respectively.

Porous SiC-mullite ceramics with high flexural strength and gas permeability prepared from photovoltaic silicon waste

In this paper, porous SiC-mullite ceramics (PSMCs) with high flexural strength and gas permeability were prepared with various mass fractions of MoO3 and Al2O3. Higher performance was achieved at low sintering temperatures and the problem of large amounts of cristobalite phase in the PSMCs was solved. The results show that 4 wt% MoO3 is optimal for the growth of mullite rods at a sintering temperature of 850 °C. Porosity was effectively controlled by the formation of interlocking structure and mechanical strength was not obviously affected. Therefore, the optimal content of Al2O3 was 25 wt% in samples prepared at 850–1200 °C, as the flexural strength was generally higher than that in samples with other Al2O3 contents. The highest flexural strength of 66.02 MPa was achieved at an open porosity of 45.4%, gas permeability of 2.32 × 10−13 m2, and permeance of 4.62 × 10−5 mol m−2 s−1 Pa−1 in samples sintered at 1000 °C. This work is of significance for the industrial preparation of PSMCs from photovoltaic silicon waste.

Anisotropic growth and photoluminescence of Li2Si2O5 hydrate rods

Herein, we developed a facile one-pot hydrothermal route to synthesize uniform functional Li2Si2O5 hydrate rod-like crystals. The growth of such unique anisotropic morphology underwent an in situ crystallization involving ordered attachment and Ostwald ripening of Li2SiO3 nanoparticles, and reactive transformation of Li2SiO3-to-Li2Si2O5 hydrate processes. The obtained Li2Si2O5 hydrate rods possessed a uniform size with a length of about 5 µm and a diameter of about 100–200 nm, indicating aspect ratio higher than 20 that reflected the anisotropic growth. The Li2Si2O5 hydrate rods exhibited excellent adsorption performance of methylene blue and the methylene blue-bearing Li2Si2O5 hydrate featured interesting photoluminescence performance of red emission at 675 nm compared with the reported value. The result endowed the Li2Si2O5 hydrate rods with a potential application as an optical probe for organic dye’s recognition.

Theoretical and numerical investigations of rod growth of an Ni–Zr eutectic alloy

In this work, the directional solidification of NiZr–NiZr $$_2$$ eutectics under isothermal conditions is investigated through numerical and theoretical means. Multiple three-dimensional phase-field simulations, including a large-scale simulation, are performed to study the free pattern selection and the velocity–spacing relation of the evolving solidification microstructures. The computed velocities for different spacings of the stoichiometric NiZr rods in the as-well stoichiometric NiZr $$_2$$ matrix are compared with the predictions of the classical Jackson–Hunt analysis. Due to certain simplifying assumptions invoked in the original theory which are not entirely representative of the numerically realized microstructures, significant deviations are observed between the two. In view of this, an extended theory is formulated accounting for the global hexagonal arrangement of the evolving rods as well as the solidification front curvatures. Owing to that, a superior compliance is achieved between the analytical and simulated growth kinetics. The key elements of symmetry incorporation are of particular importance, especially in applications to ternary systems.

Działanie in vitro olejku cyprysowego (Oleum Cupressi) na bakterie beztlenowe

Introduction. Cypress (Cupressus sempervirens L.) belongs to the family Cupressaceae. It is evergreen, and grows in Mediterranean region. The Cypress leaves and young branches are utilized to produce the essential oil. Cypress oil contain a number of components, in it α-pinene, Δ3-carene, α-terpinyl acetate, cedrol, α-terpinolene, β-myrcene, limonene, α-terpineolene, terpinen-4-ol, β-pinene, δ-cadinene and sabinene. The oil is used in therapy different diseases. It to have antimicrobial activity. Aim. The aim of the date was evaluation the susceptibility of anaerobic bacteria to Cypress oil. Material and methods. The anaerobic bacteria were isolated from patients. The 62 microorganisms, in it 36 strains of Gram-negative rods, 14 Gram-positive cocci and 12 Gram-positive rods, and 7 reference strains were tested. Susceptibility (MIC) was determined by means of plate dilution technique in Brucella agar supplemented with 5% defibrynated sheep blood, menadione and hemin. The Cypress oil was dissolved in DMSO and distilled water to obtain final following concentrations: 2.5, 5.0, 7.5, 10.0, 15.0 and 20.0 mg/ml. Inoculum containing 106 CFU per 1 ml was seeded with Steers replicator upon the agar with oil or without the oil (strains growth control). The agar plates was incubated in anaerobic condition in anaerobic jar in 37°C for 48 hrs. The MIC was interpreted as the lowest concentration of Cypress oil inhibiting the growth of tested bacteria. Results. The results indicated that from among Gram-negative rods the most susceptible to Cypress oil was the strains from genus Tannerella forsythia (MIC < 2.5-5.0 mg/ml), Bacteroides uniformis (MIC = 5.0 mg/ml), Bacteroides vulgatus and Porphyromonas asaccharolytica (MIC 5.0-7.5 mg/ml) and Porphyromonas levii (MIC = 7.5 mg/ml). The strains from genera Fusobacterium and of Bacteroides fragilis were the susceptible to 2.5-≥ 20.0 mg/ml. The Cypress oil was least active towards Prevotella and Parabacteroides strains (MIC ≥ 20.0 mg/ml).The tested Gram-positive cocci were more susceptible. The growth of the strains were inhibited by concentrations in ranges ≤ 2.5-7.5 mg/ml. The oil was minor active towards Gram-positive rods (MIC ≤ 2.5-20.0 mg/ml). Among the strains the genus of Actinomyces odontolyticus (MIC = 5.0 mg/ml) and Actinomyces viscosus (MIC ≤ 2.5-7.5 mg/ml) were the most susceptible. The growth of rods of Bifidobacterium breve was inhibited by concentrations 10.0 mg/ml. The data indicates that the Gram-negative rods were the less susceptible than Gram-positive bacteria to cypress oil. Conclusions. Among Gram-negative rods the most susceptible were the strains Tannerella forsythia, Bacteroides uniformis, Bacteroides vulgatus, Porphyromonas asaccharolytica and Porphyromonas levii. The oil was more active against Gram-positive cocci. Gram-positive anaerobic bacteria demonstrate the more susceptible to Cypress oil then Gram-positive rods.

Micro structure of hydrothermal ZnO rods on micro cantilever surface

This study reports the microstructure of Hydrothermal ZnO rods on Micro cantilever Surface. Synthesis of ZnO rods consists of two processes e.g. a formation of seed layer using Zinc asetate dihydrate by a dip-coating and a growth of the ZnO rods using Zinc-Nitrate-Tetrahydrate at temperature 95°C for time variations of 1 hours, 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours. Drying condition for both seed layer and growth of ZnO rods was done at a temperature of 120°C for 2 hours. The characterization of ZnO rods morphology was done by Field Emission-Scanning Electron Microscopy (FE-SEM), chemical element composition was performed with Energy Dispersive Spectrometry (EDS), crystal structure was done by X-ray Diffraction (XRD) and functional group analysis was done by Fourier Transform Infrared (FTIR). The characterization results show that the formation of Zinc Oxide with confirmed hexagonal form of FE-SEM and XRD results. The FE-SEM results show that the variation in growth time has an effect on the diameter size formed above the microcantilever. The longer the growth time, the larger the diameter of ZnO rods.

Preliminary Study of a New Growing Rod System in Immature Swine Model

Growing rod techniques have been demonstrated to be a valuable treatment in early-onset scoliosis; however, repeated surgeries and general anesthesia cannot be avoided. This study included 12 immature swine that were randomly assigned to receive either a novel growing rod system (experimental group) or a traditional growing rod system (control group). Lengthening was undertaken at 4-week intervals, for a total observation period of 12 weeks. Radiography, computed tomography, and motion analysis of the spine were conducted to evaluate rod extension, growth and nonfusion of the spine, and fixation. One swine (control group) was excluded from the analysis because of a deep wound infection at 1 week after the initial operation. No complications were observed in the remaining 11 swine. In the experimental group, the average lengthening operation lasted 12.1 ± 3.1 minutes, and average incision length was 1.1 ± 0.2 cm; both values were significantly less compared with the control group (P < 0.001). No significant between-group differences in mean trunk length, body mass, or thickness of cephalad-instrumented or caudad-instrumented vertebrae and intervertebral disks were present before the initial operation or at the final assessment (12 weeks after operation; P > 0.05). Spinal growth and motion of instrumented spinal segments were conserved. The novel growing rod system is safe and effective in immature swine, preserving spine growth potential and involving less surgical trauma.

In situ fabrication of ZrB2-SiC composite powders with controllable morphology by a two-step calcination method

In order to obtain controllable morphology ZrB2-SiC composite powders, a two-step calcination method (TSC) was designed to separate the formation process of ZrB2 (1300 °C) and SiC (1400 °C), which is beneficial to the growth and self-assembly of ZrB2 rods. Besides the Si content also affected the morphology of final product. The results show that in ZrB2-SiC with lower Si content, ZrB2 rods with a diameter of 1–2 μm and aspect ratios of ∼8 are randomly distributed, but with increasing Si addition, ZrB2 rods started to be oriented arrange and assembled to clusters. The ZrB2-SiC with 30 vol% SiC obtained by TSC had the ZrB2 with clusters, and spherical SiC particles well dispersed among rods.

Key Results from Detailed Nondestructive Examinations of 25 Pressurized Water Reactor High Burnup Spent Nuclear Fuel Rods

The High Burnup Spent Fuel Data Project, sponsored by the U.S. Department of Energy Office of Nuclear Energy, is focused on understanding the effects of long-term storage and transportation on high burnup (HBU) (>45 GW days per tonne uranium) light water reactor fuel. The project includes 32 HBU spent nuclear fuel (SNF) assemblies (the project assemblies) that are stored in a typical independent spent fuel storage installation (ISFSI) and 25 “sister rods”—9 SNF rods that were removed from the fuel assemblies prior to insertion to the ISFSI and 16 SNF rods removed from similar HBU assemblies. The sister rods provide a baseline of the condition of the HBU rods before loading, drying, and long-term dry storage. The project assemblies will be inspected after 10 years, and the physical state of the stored rods will be compared with the condition of the sister rods to identify any changes in physical properties during the dry storage period. This work focuses on key results from the nondestructive postirradiation examinations of the sister rods and summarizes the results of detailed visual examinations, gamma scans, dimensional measurements, and eddy current liftoff measurements of the combined Chalk River unidentified deposits and oxide layer on the waterside surface of the rod. The data are used to calculate fuel rod and pellet stack growth rates, estimated remaining fuel rod plenum volumes, and the percentage change in fuel rod cladding diameter.

Hydrothermal growth of Fe2O3 nano/micro-rods on Fe foil for Cr(VI) removal

Abstract In this work, the effect of hydrothermal duration on the synthesis of Fe2O3 rods on Fe foil was studied. The hydrothermal process was performed at 100 °C for 6–15 h. The fabricated samples were then annealed at 300 °C for 2 h. Iron oxide nano/micro-rods (diameter: 50–250 nm) which comprised of γ-Fe2O3 and α-Fe2O3 phases were successfully grown on the Fe foil after the hydrothermal process. Rise in hydrothermal duration resulted in more growth of rods on the Fe foil. After 12 h, the entire Fe substrate was fully covered with Fe2O3 rods. Hydrothermal duration of 12 h was found to be sufficient for Fe2O3 rod growth by achieving >99% of Cr(VI) removal in 50 min.

Facile synthesis of urchin-like Cs x WO3 particles with improved transparent thermal insulation using bacterial cellulose as a template.

Urchin-like CsxWO3 particles were synthesized using bacterial cellulose (BC) as a template by the hydrothermal method. The effects of the BC addition amount on the morphology, W5+ content and transparent thermal insulation of CsxWO3 were studied. It has been confirmed that abnormal growth of CsxWO3 rods was greatly reduced after introduction of BC into the precursor solution. Moreover, introduction of BC into the precursor solution could significantly improve the transparent thermal insulation properties of the CsxWO3 film. In particular, when the BC amount was appropriate, the prepared CsxWO3 film exhibited better visible transparency, with the visible light transmittance (TVis) more than 60%. In addition, the urchin-like particles could be transformed into small size nanorods after H2 heat-treatment, exhibiting excellent visible light transparency and thermal insulation performance. In particular, it has been proved that the 20BC-HT-CsxWO3 film exhibits excellent thermal insulation performance, and shows broad application prospects in the field of solar heat filters and energy-saving window glass.

Biofilm capacitance and mixed culture bacteria influence on performance of Microbial Fuel Cells-Electrochemical impedance studies

Electrochemical Impedance Spectroscopy is employed to understand the role of biological capacitance and individual component resistance in the bioelectricity generation throughout the lifetime of the microbial fuel cells. Gram stain analysis and optical microscopy supported the predominant growth of rod shaped geobacter culture in sweet lime based microbial fuel cells. The anodic capacitance during initial bacterial growth and biofilm formation (1-9 days) is 6 times higher than the literature data. The anodic capacitance decreased to 0.52mF on day 24 and anodic polarization resistance increased to913.8Ω due to fungal formation. The power density calculated on day24 being 497.1mW/m2 which is approximately 3times higher than the literature data.

Pathway-Directed Screen for Inhibitors of the Bacterial Cell Elongation Machinery.

New antibiotics are needed to combat the growing problem of resistant bacterial infections. An attractive avenue toward the discovery of such next-generation therapies is to identify novel inhibitors of clinically validated targets, like cell wall biogenesis. We have therefore developed a pathway-directed whole-cell screen for small molecules that block the activity of the Rod system of Escherichia coli This conserved multiprotein complex is required for cell elongation and the morphogenesis of rod-shaped bacteria. It is composed of cell wall synthases and membrane proteins of unknown function that are organized by filaments of the actin-like MreB protein. Our screen takes advantage of the conditional essentiality of the Rod system and the ability of the beta-lactam mecillinam (also known as amdinocillin) to cause a toxic malfunctioning of the machinery. Rod system inhibitors can therefore be identified as molecules that promote growth in the presence of mecillinam under conditions permissive for the growth of Rod- cells. A screen of ∼690,000 compounds identified 1,300 compounds that were active against E. coli Pathway-directed screening of a majority of this subset of compounds for Rod inhibitors successfully identified eight analogs of the MreB antagonist A22. Further characterization of the A22 analogs identified showed that their antibiotic activity under conditions where the Rod system is essential was strongly correlated with their ability to suppress mecillinam toxicity. This result combined with those from additional biological studies reinforce the notion that A22-like molecules are relatively specific for MreB and suggest that the lipoprotein transport factor LolA is unlikely to be a physiologically relevant target as previously proposed.

Shaping Silica Rods by Tuning Hydrolysis and Condensation of Silica Precursors.

We present the synthesis of colloidal silica particles with new shapes by manipulating the growth conditions of rods that are growing from polyvinylpyrrolidone-loaded water-rich droplets containing ammonia and ethanol. The silica rods grow by ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS). The lengthwise growth of these silica rods gives us the opportunity to change the conditions at any time during the reaction. In this work, we vary the availability of hydrolyzed monomers as a function of time and study how the change in balance between the hydrolysis and condensation reactions affects a typical synthesis (as described in more detail by our group earlier1). First, we show that in a “standard” synthesis, there are two silica growth processes occurring; one in the oil phase and one in the droplet. The growth process in the water droplet causes the lengthwise growth of the rods. The growth process in the oil phase produces a thin silica layer around the rods, but also causes the nucleation of 70 nm silica spheres. During a typical rod growth, silica formation mainly takes place in the droplet. The addition of partially hydrolyzed TEOS or tetramethoxysilane (TMOS) to the growth mixture results in a change in balance between the hydrolysis and condensation reaction. As a result, the growth also starts to take place on the surface of the water droplet and thus from the oil phase, not only from inside the droplet onto a silica rod sticking out of the droplet. Carefully tuning the growth from the droplet and the growth from the oil phase allowed us to create nanospheres, hollow silica rods, hollow sphere rod systems (colloidal matchsticks), and bent silica rods.

High-throughput growth of SmxPr1-xFeO3 all-in-one single crystal rod with quasi-continuous composition distribution

SmxPr1-xFeO3 (x = 0, 0.4, 0.7, 0.9, 1.0) all-in-one single crystal rod with quasi-continuous composition distribution was successfully grown by a hetero-seed and hetero-feed optical floating zone technique in flowing air. The lattice mismatch between each adjacent composition is very small, leading to the high-quality continuous growth of SmxPr1-xFeO3 single crystal rod. X-ray back-reflection Laue photographs indicate that all single crystals at different positions along the growth direction have good crystallization quality and the same crystallographic axis. The composition change of the quasi-continuous single crystals along growth direction was analyzed by energy-dispersive X-ray spectroscopy (EDS), which shows that the composition varies continuously and smoothly near the different composition boundaries. At a distance relatively far away from the boundary, the composition remains constant. Finally, we measured the anisotropic magnetic properties of these single crystals when x = 0.7. Our study shows that the hetero-seed and hetero-feed optical floating zone technique has a great potential for high-throughput growth of crystalline materials, and could serve as an effective method to collect single crystal material properties in materials database research.

Freezing effect of metal droplets on the vapor liquid solid growth of nanocrystal rods

Indium tin oxide (ITO) films with different temperatures were prepared by an electron beam evaporation technique. The nanocrystal rods were synthesized by vapor–liqiud–solid (VLS) crystal growth method at the higher temperature 300 °C. The surface morphology of the samples was analyzed by scanning electron microscopy (SEM). There was a metal cap on the top of the nanocrystal rod, which was the typical morphology of VLS nanocrystalrod. The structure of crystalline rods was confirmed by X-ray diffraction (XRD). Transmission electron microscopy (TEM) of the single crystalrod displayed that the lattice was uncontinuous between the top cap and the rod. Metal droplets were considered to be metallic indium tin and its alloys. The shape and composition of droplets were affected by temperature, and the metal droplets were discovered to undergo a gradual freezing process during the VLS nanocrystal rod growth.

Growth mechanism of α-Si3N4 submicron rods prepared from amorphous Si3N4 powders

Novel polycrystal α-Si3N4 submicron rods have been successfully prepared from amorphous Si3N4 powders. As-synthesized submicron rods have oblate section, with the size of 110–150 nm in height, 150–300 nm in width and 3 µm to tens of micrometers in length. Underlying growth mechanism was rationally proposed based on the results of X-ray diffraction analyses, scanning electron microscopy and transmission electron microscopy observations. It was demonstrated that the nucleation and crystal growth of α-Si3N4 occurred simultaneously during the fabrication process of submicron α-Si3N4 rods. The growth of α-Si3N4 submicron rods follows vapor-solid-solid mechanism. The submicron rods grew from the surface of amorphous Si3N4 powders in N2 atmosphere without catalysts. The silicon monoxide vapor [(SiO)g], as a reaction intermediate, reacted with nitrogen [N2] to form α-Si3N4 seeds, further growing into the Si3N4 nanowires. Finally, the Si and N atoms deposited on the surface of Si3N4 nanowires and rearranged to form submicron rods.

Model on transport phenomena and control of rod growth uniformity in siemens CVD reactor

The transport phenomena in Siemens reactors has been investigated by using computational fluid dynamics (CFD) technique. The reaction kinetics was validated against two data sets of silicon epitaxial deposition experiments. Comparative simulations were carried out for four types of reactors with different configurations of gas supplying nozzles and offgas ports. The uniformity index was introduced to evaluate rod growth uniformity. The result showed that improper gas distributing system would result in zones of low velocity together with high temperature, and uneven species concentration distribution, finally cause low uniformity of rod growth. The reactor with a single offgas port at the center of the bottom plate was supposed to be best design among the four from both the performance and the equipment complexity points of view.

The early nucleation of a eutectic alloy during high-energy milling

The nucleation of a eutectic alloy –at an early stage– and the factors that determine whether rod or hexagonal growth occurs were evaluated as a function of the process control agent (PCA)—or the lack of it. The study is subdivided into three separated experiments; in all cases, the samples (elemental powders of Pb and Sn) were processed by high-energy milling under composition, pressure and temperature (c-P-T) vial conditions. In the first case, it was detected an excessive mechanical kneading when the powders were processed without PCA and a monolith –as long as 5 mm in length– was obtained. However, this route should not be underestimated because the presence of α−, β− and eutectic-phases –at the surface of the monolith– were traced as nanoparticles (<100 nm). In the second and third cases, to prevent the excessive mechanical kneading and interparticle bond of the powders during milling, two different mechanochemical routes with PCA were considered: (i) tributyl phosphate (TBP) and (ii) ethanol (ETOH). Both of them were proposed to modify the viscoelastic behaviour of the powders. Nanorods resulted when TBP was used. Although structural disorder –at nanometric scale– was not traced, other effects associated with TBP like organic debris and the presence of by-products were detected. Based on the results with the ETOH option, it was shown that the precursors store energy as structural defects during milling. This suggests that the early eutectic nucleation (hexagonal crystal structure) occurred due to structural defects, crystals interfaces and phase boundaries. These acted as preferential sites for nucleation. Moreover, a typical eutectic phase distribution was detected. Finally, it was demonstrated that even after prolonged milling time and nonetheless the kind of PCA –or the lack of it, only the eutectic formation was scarcely traced; that is to say, a partial eutectic formation took place.

Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment.

A protocol for the aqueous synthesis of ca. 1-μm-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 °C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 °C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 °C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 °C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 °C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 °C.